The chemical control of respiration in patients with chronic obstructive pulmonary disease receiving various concentrations of inspired oxygen will be studied. In particular, the relationship of blood ammonia, cerebrospinal fluid ammonia and cerebrospinal fluid amino acid concentrations to depression of ventilation during oxygen therapy will be emphasized. Basic studies of the respiratory control system will be carried out in experimental animals, in order to develop an accurate dynamic model of the system. The ability of the carotid chemoreceptors to sustain ventilation during prolonged perfusion of the vertebral arteries with hypocapnic blood and the time course of ventilatory recovery from CO2 breathing during hypocapnic vertebral artery perfusion in both intact and peripherally chemodenervated animals will be determined. BIBLIOGRAPHIC REFERENCES: Portal blood flow and peripheral arterial NH3 concentration during systemic hypercapnia. R.A. Berkman, M.G. Levitzky, and R.E. Dutton. Fed. Proc. 34: 430, 1975 abs; Cardiopulmonary adjustments following single high dosage administration of methylprednisolone in traumatized man. J. Lozman, R.E. Dutton, M. English, and S.R. Powers, Jr. Ann. Surg. 181: 317-324, 1975.